In the so-called “mass media driven society” at the present time, a refractive-index-distributed optical molded article comprising regions of different refractive indices is in significantly great demand. As examples of such an optical molded article, optical materials such as an optical waveguide which transmits data and microlens arrays for image devices using a semiconductor such as a CCD (Charge Coupled Device) image sensor and a CMOS (Complementary Metal Oxide Semiconductor) image sensor, and an organic EL or liquid crystal display in which a high refractive index portion and a low refractive index portion are formed on a pixel to improve brightness and contrast so as to prevent color leakage between pixels as described in JP-A 2002-164180 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) are known.
An example of a method for coating and forming these two distinct regions having different refractive indices is a method comprising the steps of performing patterning with a radiation sensitive material, applying a radiation sensitive material having a different refractive index thereon and then performing patterning again. Alternatively, the regions can be formed by a method comprising the steps of performing patterning with a radiation sensitive material, applying a material having a different refractive index thereon, and performing surface polishing by a dry etching or CMP (Chemical Mechanical Planarization) process or by using a material which undergoes a change in refractive index through exposure as described in JP-A 62-25705, JP-A 7-92313 and JP-A 11-060803.
However, the methods using two types of radiation sensitive materials and the method involving surface polishing have such problems in terms of processes as complicated processes and high costs and have such a limitation that only materials suited for surface polishing can be used. As for the material whose refractive index is changed by exposure, the maximum refractive index difference is as large as about 0.001 to 0.02, and it is difficult to achieve much wider refractive index distribution for the purposes of preventing an optical loss in an optical waveguide and improving the light converging rate of microlens.